This invention relates to a pump and its manufacturing process, more particularly to a centrifugal pump formed by pressing and welding metal sheets and its manufacturing process.
Pumps for industrial purposes are a kind of general mechanical product in great need, and they are applied to a variety of industrial fields. Pumps are ordinarily manufactured by casting, which is a power-consuming, material-consuming and labor-intensive process that is capable of environmental pollution. The manufacturing of some parts of the small-flow and high-lift pumps, for example, the small-flow, narrow-impeller, is impossible by casting owing to its processing limitations. Therefore, there is research on the production of impellers with metal sheets by the pressing and welding method in order to make the pressing centrifugal pump. In some of the conventional centrifugal pumps only the impellers are formed by simply pressing and projection welding the metal sheets while the pump casings are still made by casting. Consequently, the drawbacks of the conventional casting processing cannot be completely overcome, and the process is still hard, the technical performance is poor.
Herein the said invention is motivated in consideration of how to manufacture all the parts of the centrifugal pump by pressing and welding so as to abate environmental pollution, alleviate working intensity, improve the strength of the pump casing and its technical performance, and greatly enhance the operating efficiency of the pump.
The inventor of the present invention, according to his long exposure to such fields as the development, manufacturing and processing of the pressed products, has produced an original design based on repeated research and analysis, eventually making the present invention.
Aimed at the inadequacy of the present technology, an object of the invention is to provide a pump wholly manufactured by pressing and welding process. This is a pressed centrifugal pump characterized with high strength and high operating efficiency; the strength and the rigidity of the pump casing are good enough to bear the acting force of the pipeline and the internal pressure.
Another object of the invention is to provide a manufacturing process by which all the parts of a pump are formed by pressing and welding.
The purposes of the invention can be achieved as follows: the pump casing, the impeller, labyrinth ring supports, labyrinth rings, the rear cover and the chassis of the pump are formed by pressing. It is characterized in the manufacturing process as the following steps: an openable female mold is made of wear-resistant metal. The inside of the female mold takes an integrated spiral shape of approximately 360xc2x0 and increases gradually radially outward; its cross section resembles roughly a semicircle. The internal male mold is made of pressing-deformable flexible or elastic material. The metal sheets are pressed into a tubular unit with flange, which will be inserted between the molds. Then the molds will be closed and the male mold made of the flexible or elastic material will expand so that the tubular unit will expand in the radial direction into a gradually increasing spiral case of approximately 360xc2x0 , whose cross section resembles roughly a semicircle. The above-mentioned internal male mold can be made of polyurethane rubber as the flexible or elastic material.
The pump formed by pressing in the present invention consists of an entrance flange, a discharge flange, a rear cover, a pump casing, and an impeller, characterized in that there is an integrated spiral chamber of an approximate 360xc2x0 whose cross section resembles roughly a semicircle that increases gradually radially outward in the flowing direction of the fluid between the pump casing and the impeller. Besides, there is a discharge aperture resembling an ellipse approximately, the discharge neck is joined to the discharge aperture of the pump casing.
The objectives of the present invention can be achieved through the following steps:
The axial outer surface of the joint between the pump casing and the entrance flange is a camber with a gradually increasing curvature;, the axial curvature varies in connection with the radial extending height. The larger the radial extension, the smaller the axial curvature, which makes the thickness of the plate of the various parts of the pump casing more uniform during the pressing process. Therefore, the pressure from the pipeline is more evenly sustained and at the same time the rigidity and the intensity of the pump casing display the optimum state.
The discharge neck at the aperture of the pump casing is welded on the pump casing; it resembles an ellipse and its diameter can vary. This meets the requirements of the flowing cross section of the fluid and can reduce resistance and noise, thus promoting the efficiency.
At least two evenly distributed ribs are joined to the pump casing and the entrance flange, evenly distributing the pipeline pressure onto the surface of the pump casing, and strengthening the intensity of the entrance flange. The cross section of the rib is U-shaped. It has a high stiffness and can save materials.
There are labyrinth ring supports in the pump casing which connect and support the inner side and outer side of the location where both the ribs of the entrance flange and the labyrinth ring supports sustain the pump casing, so as to make the ribs and the labyrinth supports sustain each other and also to enhance the strength of the pump casing.
The impeller comprises a front impeller plate, a rear impeller plate, and a spiral blade sandwiched between the two plates. This structure can effectively increase the strength of the impeller blade.
The space between the impeller entrance and the pump casing entrance is sealed by the labyrinth rings located in the labyrinth ring supports. In this way, the clearance between the sealing surfaces of the static-dynamic sealing is less than 0.5 millimeter, and the effect is good.
To summarize what is mentioned above, the technical characteristics of the present invention can be described as follows:
1. All the parts of the centrifugal pump are formed by pressing and welding with a simple process, by which all the parts of the centrifugal pump are made of the metal sheets with a thickness ranging from 0.5 mm to 5 mm. Compared with the same-type pump formed by casting, the weight of the said pump is a quarter of, its efficiency is 5-7% higher than, and its cost is two thirds of that of the latter. The pump saves energy and materials, its working efficiency high. The use of it can avoid environmental pollution and alleviate working intensity. The metal sheets can be made of stainless steel plates, which are rot-resistant and lasting. It can transfer heavily viscous fluid and can operate in the acid, alkali and other corrosive media in the temperature ranging from xe2x88x9240xc2x0 C. to 180xc2x0 C.
2. The manufacturing processing is subtly designed. The structure of the impeller overcomes the difficulty unsolved by the centrifugal pump formed by casting with a rotating speed Ns lower than 30 and a discharge aperture of 1-2 mm in width. The thickness of the pump casing formed by pressing is uniform; it is of an uneven, asymmetrical, spiral shape, which is more suitable for the flow of the fluids. The static-dynamic sealing between the impeller entrance and the casing entrance is sealed by labyrinth rings with a sealing clearance smaller than 0.5 mm. The discharge neck is welded on the pump casing; the welding shape resembles an ellipse and its diameter varying, leaving no scar.
3. The strength and the intensity of the centrifugal pump casing are both at their optimum states. The casing can sustain the maximal acting force from the pipeline and the internal pressure. It is widely applicable in the sites of the small-flow, high-lift transfer of fluid under pressure.